Patent Document 1 discloses that carbon dioxide is generally effective for the following symptoms (1) to (10) (see Patent Document 1):
(1) itching accompanying mucocutaneous diseases or mucocutaneous disorders such as athlete's foot, insect bite, atopic dermatitis, nummular eczema, xeroderma, seborrheic eczema, urticaria, prurigo, housewives' eczema, acne vulgaris, impetigo, folliculitis, carbuncle, furunculosis, phlegmon, pyoderma, psoriasis, ichthyosis, palmoplantar keratoderma, lichen, pityriasis, wound, burn, rhagades, erosion, and chilblain; mucocutaneous injuries such as decubitus ulcer, wound, burn, angular stomatitis, stomatitis, skin ulcer, rhagades, erosion, chilblain, and gangrene;(2) incomplete engraftment of skin grafts, skin flaps etc.;(3) dental diseases such as gingivitis, alveolar pyorrhea, denture ulcers, nigricans gingiva, and stomatitis;(4) skin ulcers, cryesthesia and numbness caused by peripheral circulatory disorders such as thromboangitis obliterans, arteriolosclerosis obliterans, diabetic peripheral circulatory disorders, and lower limb varicosis;(5) musculoskeletal diseases such as chronic rheumatoid arthritis, cervico-omo-brachial syndrome, myalgia, arthralgia and lumbago;(6) nervous system diseases such as neuralgia, polyneuritis, and subacute myelo-optic neuropathy;(7) keratoses such as psoriasis, corns, calluses, ichthyosis, palmoplantar keratoderma, lichen, and pityriasis;(8) suppurative skin diseases such as acne vulgaris, impetigo, folliculitis, carbuncles, furuncles, phlegmon, pyoderma, and suppurative eczema;(9) suppression of hair regrowth after depilation (treatment of unwanted hair); and(10) cosmetic troubles with the skin or hair such as freckles, rough skin, loss of clarity of the skin, loss of elasticity or luster of the skin, and loss of glossiness of the hair, and partial obesity.
In order to achieve an improvement of the above-mentioned symptoms, as a carbon dioxide supplying means, a composition for preparing a carbon dioxide agent for external use (see Patent Documents 2 to 3), a carbon dioxide composition for external use (see Patent Document 4), a composition for preparing a carbon dioxide gel for external use (see Patent Document 5), a material for preparing a carbon dioxide agent for external use (see Patent Document 6), and a carbon dioxide external administration device (see Patent Documents 7 to 8) are disclosed.
Furthermore, Patent Document 9 discloses reduction of pain involved in musculoskeletal disorders by transdermal introduction of carbon dioxide.
However, use of a carbon dioxide supplying means for muscle strengthening, and more particularly, a muscle strengthening agent and a muscle strength decrease inhibitor containing carbon dioxide as an active ingredient, a muscle training method and a method of increasing cattle meat which use the carbon dioxide supplying means have not been known at all.
As a muscle strengthening method, muscle training in which a target muscle is contracted by the strength of 60% or more of the maximum muscle strength is common. In addition, kaatsu (pressure) muscle training is proposed, which is said to be capable of enhancing muscle strength within a shorter period of time by pressurizing a target muscle so as to inhibit the blood flow during the exercise.
The muscle strengthening method by the above-mentioned muscle training uses a phenomenon when muscle fatigue of a certain level or more is generated, the muscle strength is increased after a certain period of time has passed. In this case, recovery from fatigue is necessary because if the recovery from muscle fatigue is slow, fatigue accumulates, thus not only reducing the effect of the muscle training but also tending to cause injury and the like. Therefore, in order to increase the efficiency of muscle strengthening, the recovery from fatigue is carried out by means of massage, low frequency therapy apparatus, warm bath, and the like, after the muscle training. However, it is reported that massage does not have an effect of promoting muscle strengthening (see Non-patent Document 1). Therefore, massage is not thought useful for the recovery from fatigue.
As a method of increasing the amount of the muscle which does not need muscle training, a method of increasing the amount of the muscle by externally applying a heat load to a living body has been proposed (see Patent Document 10). In the present invention, “muscle strengthening” and “increasing the amount of the muscle” are intended to have the same meaning.
However, the method of increasing the amount of the muscle by applying a heat load described in Patent Document 10 requires accurate temperature management because the effective temperature for obtaining the effect of increasing the amount of the muscle (38 to 41° C.) approximates to the temperature at which tissue cells are killed (43° C.). When a living body is warmed by the use of an external heat source, the temperature of the skin is the highest and the temperature becomes lower toward the inside of the living body. Therefore, it is not easy to heat only the muscle at the effective temperature for a certain period of time or more.
Furthermore, the increasing of the amount of the muscle by this method needs such a long period of time as 14 weeks in order to increase, for example, the biceps brachii by 4% even when muscle training is carried out concurrently. Thus, this method is extremely ineffective.    Patent Document 1: Patent Document: Japanese Patent Unexamined Publication No. 2000-319187    Patent Document 2: Patent Document: National Publication of International Patent Application No. 2002/80941    Patent Document 3: Patent Document: National Publication of International Patent Application No. 2006/80398    Patent Document 4: Patent Document: National Publication of International Patent Application No. 2003/57228    Patent Document 5: Patent Document: National Publication of International Patent Application No. 2005/16290    Patent Document 6: Patent Document: National Publication of International Patent Application No. 2004/4745    Patent Document 7: Patent Document: National Publication of International Patent Application No. 2004/2393    Patent Document 8: Patent Document: National Publication of International Patent Application No. 2008/047829    Patent Document 9: Patent Document: U.S. Pat. No. 6,652,479B2    Patent Document 10: Patent Document: Japanese Patent Unexamined Publication No. 2006-61687    Non-patent Document 1: Non-patent Document 1: Sven Joenhagen et al., Sports Massage After Eccentric Exercise. The American Journal of Sports Medicine. 2004; 6: 1499-1503